Transcript for Third American Airlines Flight Forced to Land Over Unbolted Seats

Good I had come on here we learned it has happened again a third American Airlines flight forced to land after a row of seats came unbolted. Half of their fleet of 750 sevens were grounded for inspection most of them now back in service but isn't so. There have been a flurry of cancellations. And delays. So what do you do if you're booking a flight and what is American Airlines saying tonight about the clues they found. ABC senior national correspondent -- novel tells us. Boston's Logan field one of American's Boeing 750 sevens 47 of which nearly half the fleet taken out of service overnight and into today as the troubled airline tries to make sure no more of its coach seats come loose in flight. As they have three separate times. Certainly for fourteen. -- -- -- -- -- -- -- Somehow in the installation processes of of our seats. We images of -- -- not serve as a mechanical failure or human very. Americans saying today it is identified what caused three of its flights to be aborted in mid flight because seats came loose in one case flipping passengers on their backs. The seats -- rows of three and the -- was held -- the floor with what's called a saddle clamp. It's -- clamp that was improperly installed on the plains with a seats disengaged. On the safety side of this particular situation Americans doing all that it can do right now to ensure that those seats. Our. Being looked down and making sure that -- install this correctly as they're supposed to be. American says the investigation is still under way but so far the airline cannot give a solid answer as to -- now. These seats have been in use for up to twenty years and never come loose before. Aviation sources say the last eyes and hands on the saddle -- in all three Lucy incidents belonged to company mechanics. Leading to suspicions of possible sabotage but safety experts tell ABC news that would be -- First to deliberately think that somebody would do something to -- a seat track assemble -- -- cause it to come loose during flight it's just something that's not thought of in this industry. The mechanics union which lost jobs to outsourcing says it has had nothing to do with the lose seats. And points to the new private maintenance just the latest series of labor troubles for American Airlines which has suffered more than 2200 delays. And 75 cancellations. On time only 57% of the time. Over the last three days. More than double the delays for united and delta which are both punctual more than 80% of the time. It's gonna take American -- some time to rebuild trust in terms of the reliability of the schedule. American Airlines -- on the record it is ruled out sabotage they believe the installation mistakes of the result of human or mechanical errors. One interesting note behind American's decision to inspect all of its planes of this type of seats. One of the C rose that was loose was loose for six days with the flights without being noticed so should you take an American Airlines flight accident question he has the experts are telling us. That if you can be flexible and don't have to be some place on time it's okay it's safe just not very dependable as far as -- -- -- back on the story and I thanked him and we.

This transcript has been automatically generated and may not be 100% accurate.

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